The stopping boundaries based on Thall and Simon's criterion.

1 | ```
stopbound_post(theta, type, nmax, alpha_e, beta_e, alpha_s, beta_s, delta)
``` |

`theta` |
the cutoff probability: typically, |

`type` |
type of boundaries: "superiority" or "futility". |

`nmax` |
the maximum number of patients treated by the experimental drug. |

`alpha_e` |
the hyperparameter (shape1) of the Beta prior for the experimental drug. |

`beta_e` |
the hyperparameter (shape2) of the Beta prior for the experimental drug. |

`alpha_s` |
the hyperparameter (shape1) of the Beta prior for the standard drug. |

`beta_s` |
the hyperparameter (shape2) of the Beta prior for the standard drug. |

`delta` |
the minimally acceptable increment of the response rate for the experimental drug compared with the standard drug. Note: if type = "superiority", then delta is set to 0. |

`boundset` |
the boundaries set; |

Thall, P. F., Simon, R. (1994).
Practical Bayesian guidelines for phase IIB clinical trials.
*Biometrics* **50**: 337-349.

Yin, G. (2012).
*Clinical Trial Design: Bayesian and Frequentist Adaptive Methods.*
New York: Wiley.

1 2 3 | ```
stopbound_post(0.05, "futility", 40, 0.6, 1.4, 15, 35, 0)
stopbound_post(0.05, "futility", 30, 0.4, 1.6, 10, 40, 0)
stopbound_post(0.95, "superiority", 40, 0.6, 1.4, 15, 35, 0)
``` |

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